Refractory fibers (of predominately aluminosilicate composition), mineral wool fibers and other kinds of fibers are commonly manufactured by impinging a molten stream of the fiber forming materials on spinners or rotors which are rotating at high speed, see, e.g., U.S. Pat. Nos. 2,388,935; 2,428,810; 2,520,168; 2,520,169; 2,561,843; 2,632,919 and 3,159,475. (For convenience the discussions below will be in terms of inorganic, e.g. refractory, fibers. However, as will be noted, the invention may also be applicable to some organic fibers.) The high surface speed of the rapidly spinning rotors breaks up the molten stream into small drops and throws these drops at high velocity from the rim of the rotors. Since the drops are still molten they rapidly attenuate into fine filaments or fibers. These drops, however, also cool rapidly so that usually a portion of each drop solidifies before the drop can be completely attenuated. This solidified nonfibrous material is known as "shot" and is considered very undesirable in the collected fiber, for it gives the resulting fiber body a gritty feel and also reduces the thermal resistance of the body. Some of the larger shot particles break free from the fibers by themselves. In addition, a number of techniques have been developed to separate shot from fiber so that the latter can be separately collected; see, e.g., U.S. Pat. Nos. 2,968,069; 2,991,499 and 3,142,869. In addition to the separated shot, "waste" collected will also include coarse fibers and even some fine fibers which are carried away from the main fiber stream with the shot and coarse fiber during shot separation. Conventional practice in the past has been to allow the waste to drop into a dry collection hopper positioned below the level of the fiberizing rotors and within the fiberizing unit enclosure. When the hopper has become filled with waste, it is necessary to open the unit enclosure and remove the filled hopper (usually using a forklift truck) and replace it with an empty hopper. This procedure has several disadvantages: (1) opening of the fiberizing unit enclosure seriously disrupts the air flow through the fiber collection region and causes undesirable variations in the fiber product being collected; (2) the waste hoppers fill relatively rapidly and therefore must be replaced frequently, thus requiring a significant amount of a workman's time; (3) since the hoppers must be exchanged while the unit continues to run, the workman doing the exchanging is constantly exposed to a rain of hot shot granules falling from the rotors above the hopper location. In addition, since the waste collected contains significant quantities of fibers, it is not directly suitable for recycle and remelting.
During the course of operation of the fiberizing unit it is often necessary to remove the rotors temporarily from their position directly below the melt stream. Such an occasion may occur, for instance, when the rotors must be repaired, when there is a breakdown at the fiber collection end of the production unit or when one set of rotors is to be replaced by another. While the rotors are out of position, the melt stream pours directly down into the waste collection hopper, a procedure commonly referred to as "slagging off." Normally when slagging off is occurring the waste collection hopper is at least partially filled with water so that the molten material will solidify and break up into pieces. The cooled and broken material ("cullet") frequently contains large lumps or pieces which cannot be readily reclaimed in a form suitable for remelting.
The wet cullet collection hopper must also be changed periodically if slagging off continues for prolonged time. The much larger and hotter quantity of material involved and the amount of water present make changing the wet cullet collection hoppers a more dangerous procedure than changing the dry waste hoppers. Additionally, once the rotors are replaced in position and fiberization resumes, it is necessary to replace the wet cullet collection hopper with the dry waste collection hopper.
From the above it will be apparent that it would be desirable to have a collection system which would have a number of features: (1) it could be operated dry to collect waste; (2) it could be rapidly converted to a wet system to collect cullet; (3) it could be operated in a manner such that the waste and cullet collected would be usuable as or suitable for conversion to "reclaim," the form of scrap which is suitable for remelting; (4) it could be operated such that material collected could be continuously removed from the collection area and conveyed to a second collection point located away from the fiberization unit, so that frequent replacement of collection hoppers would be unnecessary, workmen would not be exposed to either hot shot or hot cullet, and the fiberization unit enclosure would not have to be repeatedly opened and closed with the attendant disruption of the fiber collection process; and (5) the operation could be automatically controlled such that the unit could respond to either shot formation conditions or slagging off conditions. To achieve these ends are objects of the present invention.